In some vehicles, an engine may be coupled to an alternator to generate electrical power for various components. For example, a locomotive or a generator car may include a head-end-power or hotel-electric-power (HEP) alternator that distributes electrical power to other cars in a train for lighting, electrical, and other hotel needs of passengers. More particularly, the HEP alternator may provide electrical power through a bus to an inverter circuit. For example, the inverter circuit may include dual inverters that convert direct current (DC) power from the bus to alternating current (AC) power that is provided to other cars and various electrical components.
In one example, the dual inverter circuit may be controlled by a three-position transfer switch circuit that enables the dual inverters to operate in parallel, or each in standalone operation depending on operating conditions. FIGS. 11-12 show a PRIOR ART transfer switch circuit 1100 in different operating positions. FIG. 11 shows the transfer switch circuit 1100 in a parallel operating position (e.g., middle position) where power is provided from each of a first inverter 1102 and a second inverter 1108 to a load 1114. In particular, the first inverter 1102 provides power through a first contact 1104 and through a first inductor 1106 to the load 1114. Further, the second inverter 1108 provides power through a second contact 1110 and through a second inductor 1112 to the load 1114.
FIG. 12 shows the transfer switch circuit 1100 in a standalone operating position (e.g., top position) where power is provided from the first inverter 1102 to the load 1114. In this position, the second inverter 1108 does not provide power to the load 1114. In particular, the first inverter 1102 provides power through a third contact 1116 and through the first inductor 1106 to the load 1114.
In some cases, a power transfer capability of the transfer switch circuit 1100 may be restricted due to the layout of the transfer switch. For example, when the transfer switch circuit 1100 is in the standalone operating position, all of the power from the first inverter (and the bus) passes through the third contact 1116 and first inductor 1106. In other words, the power transfer circuit 1100 provides no current sharing capabilities between contacts while in the standalone operating position. Moreover, the power transfer circuit 1100 provides no current sharing capabilities between inductors while in the standalone operating position. Because of such power demands on the single contact of the transfer switch and the single inductor while in the standalone operation position, power transferred through the switch to the load may be restricted in order to reduce the likelihood of degradation of that contact and the inductor.